Question

In the E. bowluh plant, you are investigating the inheritance of height, trunk diameter, and leaf color. Listed below are the results of your dihybrid testcrosses, each of which generated 100 offspring.

dihybrid testcross for height and trunk diameter

phenotype	number of offspring
tall, large diameter	25
tall, small diameter	24
short, large diameter	26
short, small diameter	25

dihybrid testcross for trunk diameter and leaf color

phenotype	number of offspring
large diameter, green leaves	26
small diameter, yellow leaves	23
large diameter, yellow leaves	27
small diameter, green leaves	24

dihybrid testcross for height and leaf color

phenotype	number of offspring
tall, green leaves	42
tall, yellow leaves	8
short, yellow leaves	43
short, green leaves	7

a) Which of these genes are linked? Which are unlinked?

b) How did you know that?

c) For those genes are that linked, what are the recombinant phenotypes? And how did you know that?

Answer 1

a.HEight and leaf color genes are linked. .

Unlinked genes are height gene, diameter gene and diameter , leaf color are unlinked. That is why the test cross between them resulted in nearly 1:1:1:1 ratio of the all the four combinations in the offspring.

b. Height and leaf color are linked because the test cross between the height and leaf color is not giving 1:1:1:1 ratio in the offspring. Tall and green leaf combination and short and yellow leaf combinations are much more than the tall, yellow and short ,green offspring. Parental combinations are 85% and new combinations are only 15%.

HEight gene, diameter gene and diameter , keaf color gene are unlinked because the test cross done between them is giving 1:1:1:1 ratio.

c. Tall , yellow leaves and short ,green leaves are the recombinant offspring. This is because the number of offspring is much less compared to other two phenotypes.